Can I say that what suggests seems to make sense - except I would be wary of attempting to seal an older property to that degree.
Wary does not mean I wouldn't do it though, but I'd make sure I understood the technology used in the build and the level of insulation in the original design as well as any later additions.
The reason for this is that firstly, sealing a house removes the "natural" interstitial draughts/gale force winds in the lounge we all used know and love when we were growing up in older properties.
Thus there is more moisture to deal with inside the house.
Secondly, insulating the house must be done evenly, in the sense that highly insulating one part of the house can make another seem relatively colder.
A place that previously didn't have a problem may experience the effects of damp through condensation on colder surfaces.
I think the energy audit suggested by is an excellent idea.
You should couple this with an overall set of proposals for upgrading the property in an integrated way in a properly sequenced upgrade.
Some things just go together, for example:
Passive insulation measures can be installed any time.
However insulating an attic at 1st floor ceiling level means that the rest of the space above the insulation level gets proportionally colder.
This is because most of the heat that used to escape into the attic is now held in by the insulation.
Insulating without installing a vapour check of some kind on the warm side will allow warm moist air from below to migrate into the attic space.
As it passes through the insulation layer this is likely to turn into cold damp air.
This may in turn end up depositing moisture on these colder surfaces up there and in the top layer of the insulation.
So the attic may in fact need more ventilation than it originally had.
You can install this either by adding vent tiles or slates to the roof or Glidevale or similar vent to the eaves.
The idea is to get cross ventilation if possible, and ventilate both at high and low level on the roofscape to help promote air circulation.
Its stands to reason then that after insulating at ceiling level you have to insulate service pipes and the water tank, but not beneath the tank.
Insulation of items like wall should include all the external envelope that is classed as "wall".
This means the window reveals must be insulated at the same time as the wall surfaces.
Otherwise they'll likely become cold and attract condensation.
Insulation can be internal or external but watch for cold bridges at the usual critical junctions
- Eaves
- Ope Head
- Ope Sill
- Threshold
There is littler or no point installing a MVHR system in an unsealed house - it'll run very inefficiently.
There is no way you should tightly seal an old house without installing an MHVR system - how would you vent it?
BTW before you do any "new" sealing of the house, have it pressure tested as is.
One of the speakers at Plan Expo 2009 - I think it was Joseph Little Architect- produced some empirical test results.
1940-1960's houses built using the old wet plaster finish on internal walls fared far better than might have been expected.
I think they had had new windows and doors fitted and perhaps the vents had been all taped up for the duration of the test.
Unfortunately Part F of the Building Regulations still has to catch up with Part L and also Appendix Q of the DEAP documentation.
Houses need permenant vents to habitable rooms - in Theory.
BTW Catharlach, I think its either Céadlach or Aonlach by now [either hundreds of lakes or they've all joined up into one lake].
ONQ.